THE PLANT CELL, Vol 1, Issue 3 351-360, Copyright © 1989 by American Society of Plant Biologists
The Rice Phytochrome Gene: Structure, Autoregulated Expression, and Binding of GT-1 to a Conserved Site in the 5[prime] Upstream Region
S. A. Kay, B. Keith, K. Shinozaki, M. L. Chye and N. H. Chua
The Laboratory of Plant Molecular Biology, The Rockefeller University, New York, New York 10021-6399
We have isolated and characterized both cDNA and genomic clones encoding
the apoprotein of rice phytochrome. The mRNA produced from this gene is
expressed at a low level in etiolated leaves. Following a flash of red
light, the steady-state mRNA level decreases within 15 minutes, and is
barely detectable after 2 hours. This effect is partially reversed by far
red light demonstrating autoregulation of phytochrome mRNA levels. Nuclear
run-on experiments show that this effect is exerted on transcription of the
phytochrome gene. In etiolated plants, phytochrome mRNA is twofold higher
in leaves than in roots, whereas the reverse is true in fully green plants
where phytochrome mRNA accumulates despite illumination of the leaves. DNA
gel blots and screening of libraries indicate the presence of only a single
gene, allowing convenient study of the autoregulatory phenomenon for a
specific phytochrome gene. Gel retardation analysis using a fragment from
the 5[prime] upstream region reveals that GT-1 is present in nuclear
extracts of etiolated rice leaves and binds to sites conserved between rice
and oat phytochrome genes.